Process of removing scale from boilers.



Patented Nov. I3, |900.

No.'s6|,a73. Y E. n. HoPcnoF-T.

PROCESS 0F REMOVING SCALE FROM BOILERS.

Appucacion med Apr. 37, 1899.)

(No Model.)

2 Sheets-Sheet I.

No.6|,873. Patented Nov. I3, |900.

E. D. HOPCROFT.

PROCESS 0F BEMOVINGSGALE FROM BOILERS.

(Application filed Apr. 27, 1899.)

2 Sheets-Sheet 2.

(N o Model.)

:ma Nnnnls Prrsns co. Pno'ro-LITHQ. wAsHlNsYoN, n c.

UNITED STATES ATENT Brion,

ERNEST DIGBY I-IOPCROET, OF KIDDERMINSTER, ENGLAND.

PROCESS OFv REIVIOVING` SCALE FROM BOILERS.

SPECIFICATION forming part of Letters Patent No. 661,873, dated November 13, 1900. Application led April 2*'7, 1899. Serial No, '714,7 68. (No specimens.)

To all whom, it may concer-71,:

Beit known that I, ERNEST DIGBY Hor- CROFT, boiler inspector, a subj ect of the Queen of Great Britain, and a residentl of Farlield, Kidderminster, in the county of Worcester, England, have invented a certain new and useful Improvement in a new or Improved Process of Removing Scale from Boilers, (for which I have applied forA a patent in Great Britain, No. 20,728, dated October l, A. D. 1898,) of which the followingis a specification.

My invention has for its object a new or improved process for removing scale from boilers, which is equally applicable to all kinds of boilers,whethertubularor otherwise, as well as to steam condensers, economizers, and other similar apparatus, by which the scale is readily removed from those parts of the interior surface of the boiler upon which it has accumulated, including the interior of tubes and other parts hitherto inaccessible, and this is effected without recourse to the expensive processes now in use and without removing the boiler from its bed or position, while at the same time the use of antiscale solutions is thereby obviated. Y

In order that my invention may be clearly understood and more easily carried into practice, I have appended hereunto two sheets of drawings upon which I have illustrated the application of my process to an ordinary vertical boiler, and from which its application to other forms of boiler and other apparatus will readily be understood.

'Figure l is a vertical section through a boiler and through the apparatus for removing the scale therefrom. Fig. 2 is a plan of a similar boiler, but showing a modification in the apparatus suitable for use when dealing with certain classes of scale.

In carrying my invention into eect I first empty the boiler of all superfluous moisture and afterward lower the temperature of the interior to below freezing. I generally, however, ind it necessary to lower the temperature to below 25o Fahrenheit, the variations of the requirement being rendered necessary by the different character and thickness of the various scales as well as by the quantity of surface to be dealt with, While at the same time it is important that as far as possible an even temperature shall be maintained over the whole area of the boiler required to be treated.

I believe the action of removing the scale which takes place to be as follows: During the formation of the scale the whole of the metal in the boiler is in a state of expansion, with the result that upon cooling down to a natural temperature the metal is contracted while the scale remains in its original condi- Lion; but upon lowering the temperature within the' boiler to, say, 15 or 25 Fahrenheit the metal of the boiler is further contracted, and as the scale is not affected by the lowering of the temperature in the same way or to the same extent as the metal the 'scale is broken up and separated from the metal. During the process of contraction of the metal I believe that the natural moisture contained in most classes of scale is expanded by the lower temperature which I provide, and that therefore the eXtra contraction of the metal in combination with the expansion of the scale, which combination is effected by my improved process, is responsible for the easy removal of the scale from the surface of the metal.

I will now proceed with reference to Fig. I to describe one method of obtaining and evenlydistributing the temperature required in the ordinary vertical boiler illustrated by A, in connection with which the compressor B, condenser C, and cooling-chamber D form part. The compressor B may be of any wellknown form, such as hereillustrated, having plunger b3 and cylinder b4, with inlet-valve ZJ' and outlet-valve b2, the latter of which is connected with the condenser-coil C at c'. This coil C is in turn connected with the pipe `c incooling-chamber D, and from thence a series of circulating-coils E pass to the pipe e2, which is connected with the inlet-valve b of the compressor. The condenser-tank o2 is supplied with water at E, which passes olf again at F, and a centrifugal pump H is provided in the air-cooling chamber D for raising the chlorid of calcium J into troughs h', which are placed over each circulatingcoil E and perforated for the chlorid of calcium to drip onto the members of the coil, and thereby prevent the accumulation of frost on the pipes. The air-cooling chamber D is provided with the air-propeller K, the

IOO

outlet 7a of which is connected to the .boiler through ythe hand-doors d and a2 by the flexible pipes k2 and k3. The compressor B is provided with stop-valves P and R and is driven by any suitable means, such as the driving-band b1?, as also the centrifugalV pump case of boilers of the Lancashire or Cornish type may be effected by the introduction of Open vessels, cylinders, or drums containing the liquefied air, or in cases of small boilers I may introduce the same into the boiler at various points by means of the hand-holes or ii and air-propeller Ii, which are respectively driven by the bands 71,2 and h4. The act-ion of the apparatus for the lowering of the temperature in tbe boiler Ais as follows: The compressor, condenser, and cooling-chamber coils being charged with NH3 or other suitable gases the circulation, as indicated by the arrows, is set up by the action'of the compressor, with the consequent cooling of the air in the chamber D. The cold air is then drawn from the chamber D and propelled into the boiler A at any convenient point or points, such as the hand-holes a and d2, but in such a manner as to get the distribution of the .temperature over that portion of the boiler l direct with the lower part of the boiler A, as

shown at c3, Fig. 2, in which case the boiler.

is connected near the top with the compressor B by pipepz, by which the NI-I3 or other gases may be expanded into the boiler, in which case I first create a vacuum in the boiler of, say, from thirty to thirty-threeinches. To effect this, I open valve P and draw spindle of valve 'l for discharge of air, all the other valves being closed, thus by means of the compressor creating a vacuum in the boiler, after which I close discharge-valve T and open valve R' and regulate the quantity of gas entering the boiler by the regulating-valve Y. The valve W and cylinder X containing gas are for .charging the machine.

In cases where it is desirable to rst test the boiler by air-pressure the valves R and P' are closed, valve V is open for the admission of the air, and valves T and are open, by which the air is conveyed to boiler by pipe p2.

I may obtain the required reduction in the temperature by liquefied air, which in the valve connections, and 1n most cases I prefer to work with a closed boiler under pressure of the gas formed by the pressure of the liquefied air.

In some cases where motive power is difIicult and expensive to obtain for the working of the refrigerating apparatus I may effect the required reduction of temperature by the use of chlorids or freezing mixtures applied in a similar manner to that described with reference to liquefied air. A

In classes of scale having fifteen or more per cent. of salt I iind it necessary to coat the scale with a solution of sal-ammoniac.

The form or shape of my refrigerating apparatus and the particular mode of application are immaterial to the effect and may be adapted to the local circumstances and situation so long as they are capable of producing and evenly distributing the required change of temperature, as hereinbefore set forth.

For purposes of ready transport I prefer to build up my compressor, condenser, and cooling-chamber with a motor complete upon a suitable carriage, by which it may be readily conveyed to the various boilers requiring to Aloe scaled. Y p

Having' now described my invention, what I caim as new, and desire to secure by Letters Patent, is` r 1. The process for removing scale from boilers which consists in applying to the boiler a temperature below7 the freezing-point artificially produced and snfiicient to effect the separation of the scale from the boiler.

2. A process for removing the scale from boilers, which consists of artiiicially lowering the temperature of the interior of the boiler from five to twenty degreesbelow freezingpoint, to canse a contraction ofthe metal of the boiler, and an expansion of the scale to effect a separation of the scale from the boiler, substantially as specified. l

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

ERNEST DIGBY HOPGROFT.

Witnesses:

WALTER H. BARTLAND, Lewis WM. J ooLU. 

